1. Field of the Invention
The present invention relates to a vein imaging apparatus, a positional displacement interpolation method, and a program.
2. Description of the Related Art
Biometric individual authentication is highly important technology for protecting the rights in the future network society. In commercial transactions conducted on the Internet in which money, contents, and rights can be stolen any time over the network by means of spoofing, biometric individual authentications particularly attract attention as a technique for protecting a field that may not be protected by encryption alone. However, a biometric individual authentication using fingerprint and iris may not solve the issue of counterfeiting. With regard to this issue, an individual authentication technique using a part of the vein pattern that may not be easily imaged from the outside is expected to be a biometric individual authentication for the next generation because of accuracy of determination and difficulty for counterfeiting and spoofing.
On the other hand, in developing an imaging method for taking a vein image, it is difficult to produce an imaging device with a planar structure because the position of a light source is strictly restricted. In order to solve this issue, there has been suggested a method using a wide-angle lens and the like. However, even with this method, it is difficult to limit the distance between a finger and the imaging device, and the user is required to surely place the finger at the same distance. Therefore, the reproducibility of the authentication may not be ensured. A contact or non-contact device with a large sensor is ideal in principle, but the large sensor size results in increasing the cost due to expensive optical materials. In addition, in some types of optical components for the large sensor, there is also an issue of displacement of the arrangement between the optical components and the large sensor due to thermal expansion.
In order to solve the positional displacement caused by thermal expansion among the above-described issues, for example, Japanese Patent Application Laid-Open No. 2004-296531 describes a technique for detecting the amount of positional displacement caused by thermal expansion and directly controlling the position of an optical component based on the amount of positional displacement.